Drive force output apparatus for vehicle

ABSTRACT

An engine shaft of an engine, rotatable shafts of motor generators and a drive force output shaft are interconnected with each other through a drive force transmission arrangement. An ECU computes a torque command value of each of the motor generators through use of an equation of torque equilibrium, which corresponds to the drive force transmission arrangement, based on an engine shaft demand motor generator torque and an output shaft demand motor generator torque.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by referenceJapanese Patent Application No. 2012-3222 filed on Jan. 11, 2012.

TECHNICAL FIELD

The present disclosure relates to a drive force output apparatus of avehicle.

BACKGROUND

Lately, a hybrid vehicle, which has an internal combustion engine and amotor generator(s) as drive sources of the vehicle, attracts attentionbecause of increased public demands of low fuel consumption and lowexhaust emissions. For example, JP H07-135701A teaches a hybrid vehicle,which has an internal combustion engine and first and second motorgenerators. A drive force of the engine is divided to two systemsthrough a planetary gear mechanism. An output of one of the systems isused to drive a drive shaft to drive wheels of the vehicle. Furthermore,an output of the other one of the systems is used to drive the firstmotor generator to generate an electric power. The electric powergenerated by the first motor generator and/or electric power suppliedfrom a battery is used to drive the second motor generator to enabledriving of the drive shaft with the power supplied from the second motorgenerator.

In the hybrid vehicle, which has the engine and the two motorgenerators, it is demanded to achieve three objectives, i.e., (1)controlling of the rotational speed of the engine, (2) controlling ofthe output torque and (3) limiting of input and output of the electricpower at the battery. However, in the system, in which the engine shaft(an output shaft of the engine) and the drive force output shaft arecoupled with each other through a drive force transmission arrangement,which has, for example, the planetary gear mechanism(s), when the twomotor generators are individually controlled without integrallycontrolling the two motor generators, the above-specified threeobjectives may not be achieved, or the control operation of the motorgenerators become complicated. For instance, in a system, which has twoplanetary gear mechanisms, the above-specified three objectives may notbe achieved. Also, in a system, which has a single planetary gearmechanism, the control operation of the motor generators may becomeextremely complicated.

SUMMARY

The present disclosure is made in view of the above disadvantages.According to the present disclosure, there is provided a drive forceoutput apparatus for a vehicle, including an internal combustion engine,a plurality of motor generators, a drive force transmission arrangement,a battery, an engine shaft demand motor generator torque computingsection, an output shaft demand motor generator torque computing sectionand a motor generator torque command value computing section. The driveforce transmission arrangement includes at least one drive forcedividing mechanism. An engine shaft of the internal combustion engine,rotatable shafts of the plurality of motor generators and a drive forceoutput shaft are interconnected with each other through the drive forcetransmission arrangement in a manner that enables transmission of adrive force through the drive force transmission arrangement, and thedrive force output shaft is connected to a plurality of wheels of thevehicle to transmit a drive force. The battery is connected to theplurality of motor generators to output and receive an electric powerrelative to the plurality of motor generators. The engine shaft demandmotor generator torque computing section computes an engine shaft demandmotor generator torque, which is a torque that is provided from theplurality of motor generators and is required by the engine shaft of theinternal combustion engine to control a rotational speed of the internalcombustion engine. The output shaft demand motor generator torquecomputing section computes an output shaft demand motor generatortorque, which is a torque that is provided from the plurality of motorgenerators and is required by the drive force output shaft to ensuresupply of a required drive force of the vehicle and to limit input andoutput of the battery. The motor generator torque command valuecomputing section computes a torque command value of each of theplurality of motor generators through use of an equation of torqueequilibrium, which corresponds to the drive force transmissionarrangement, based on the engine shaft demand motor generator torque andthe output shaft demand motor generator torque.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a schematic diagram showing a structure of a drive system of avehicle according to a first embodiment of the present disclosure;

FIG. 2 is a block diagram (part 1) showing a function of computing atorque command value of each motor generator according to the firstembodiment;

FIG. 3 is a block diagram (part 2) showing the function of computing thetorque command value of each motor generator according to the firstembodiment;

FIG. 4 is a flowchart showing a flow of an engine shaft demand MG torquecomputation routine of the first embodiment;

FIG. 5 is a flowchart showing a flow of an output shaft demand MG torquecomputation routine of the first embodiment;

FIG. 6 is a flowchart showing a drive source distribution routine of thefirst embodiment;

FIG. 7 is a flowchart showing an output shaft torque limit amountcomputation routine of the first embodiment;

FIG. 8 is a flowchart showing a mechanical brake cooperative controlroutine of the first embodiment;

FIG. 9 is a flowchart showing a flow of an MG torque command valuecomputation routine of the first embodiment;

FIG. 10 is a schematic diagram showing a structure of a drive forcetransmission arrangement and therearound according to a secondembodiment of the present disclosure;

FIG. 11 is a schematic diagram showing a structure of a drive forcetransmission arrangement and therearound according to a third embodimentof the present disclosure;

FIG. 12 is a schematic diagram showing a structure of a drive forcetransmission arrangement and therearound according to a fourthembodiment of the present disclosure;

FIG. 13 is a schematic diagram showing a structure of a drive forcetransmission arrangement and therearound according to a fifth embodimentof the present disclosure;

FIG. 14 is a schematic diagram showing an example of a structure of adrive force transmission arrangement and therearound according to asixth embodiment of the present disclosure;

FIG. 15 is a schematic diagram showing another example of the structureof the drive force transmission arrangement and therearound according tothe sixth embodiment of the present disclosure;

FIG. 16 is a block diagram showing a function of computing a torquecommand value of each MG according to the sixth embodiment;

FIG. 17 is a schematic diagram showing an example of a structure of adrive force transmission arrangement and therearound according to aseventh embodiment of the present disclosure;

FIG. 18 is a schematic diagram showing another example of the structureof the drive force transmission arrangement and therearound according tothe seventh embodiment of the present disclosure;

FIG. 19 is a schematic diagram showing a structure of a drive forcetransmission arrangement and therearound according to an eighthembodiment of the present disclosure; and

FIG. 20 is a schematic diagram showing a structure of a drive forcetransmission arrangement and therearound according to a ninth embodimentof the present disclosure.

DETAILED DESCRIPTION

Various embodiments of the present disclosure will be described withreference to the accompanying drawings.

First Embodiment

A first embodiment of the present disclosure will be described withreference to FIGS. 1 to 9.

First, an entire structure of a drive system (drive force outputapparatus) of a vehicle (more specifically, an automobile) of thepresent embodiment will be described with reference to FIG. 1.

An internal combustion engine 10, a first motor generator (hereinafterreferred to as a first MG) 11, a second motor generator (hereinafterreferred to as a second MG) 12 and a drive force transmissionarrangement 15 are installed to the vehicle. In the followingdescription, the term of motor generator may be abbreviated as “MG” forthe sake of simplicity. The drive force transmission arrangement 15includes a first planetary gear mechanism (a drive-force dividingmechanism) 13 and a second planetary gear mechanism (a drive-forcedividing mechanism) 14. The first MG 11 is mainly used as an electricgenerator (power generator) but is also used as an electric motor. Incontrast, the second MG 12 is mainly used as an electric motor but isalso used as an electric generator (power generator).

Each of the first and second planetary gear mechanisms 13, 14 includes asun gear S, a plurality of planetary gears, a planetary carrier C and aring gear R. In each planetary gear mechanism 13, 14, the sun gear Srotates about a central axis thereof, and each of the planetary gearsrotates about a central axis thereof and revolves around the sun gear S.Furthermore, the planetary carrier C rotates integrally with theplanetary gears, and the ring gear R is placed on a radially outer sideof the planetary gears and rotates around the planetary gears.

In the drive force transmission arrangement 15, an engine shaft 16 (anoutput shaft) of the engine 10 and the planetary carrier C of the firstplanetary gear mechanism 13 are interconnected with each other in amanner that enables conduction of the drive force therebetween. The sungear S of the first planetary gear mechanism 13, the sun gear S of thesecond planetary gear mechanism 14 and a rotatable shaft 11 a of thefirst MG 11 are interconnected with each other in a manner that enablesconduction of the drive force therebetween. Furthermore, the ring gear Rof the first planetary gear mechanism 13, the planetary carrier C of thesecond planetary gear mechanism 14 and a drive force output shaft 17 areinterconnected with each other in a manner that enables conduction ofthe drive force therebetween, and the ring gear R of the secondplanetary gear mechanism 14 and a rotatable shaft 12 a of the second MG12 are interconnected with each other in a manner that enablesconduction of the drive force therebetween. The drive force of the driveforce output shaft 17 is conducted to wheels 20 of the vehicle through adifferential gear mechanism 18 and an axle 19.

Furthermore, a first inverter 21, which drives the first MG 11, and asecond inverter 22, which drives the second MG 12, are provided. Thefirst MG 11 and the second MG 12 are connected to a battery 23 throughthe inverters 21, 22, respectively, to output and receive the electricpower relative to the battery 23, i.e., to output the electric power toand to receive the electric power from the battery 23. Furthermore, thefirst MG 11 and the second MG 12 are interconnected with each other tooutput and receive the electric power therebetween through the inverters21, 22.

A hybrid ECU 24 is a computer, which controls the entire vehicle. Thehybrid ECU 24 receives output signals from various sensors and switchesto sense the driving state of the vehicle. These sensors and switchesinclude, for example, an accelerator sensor 25, a shift switch 26, abrake sensor 27 and a vehicle speed sensor 28. The accelerator sensor 25senses a degree of depression of an accelerator pedal (also referred toas the amount of depression of the accelerator pedal or an acceleratoropening degree). The shift switch 26 senses a shift position (anoperational position of a shift lever). The brake sensor 27 senses adegree of depression of a brake pedal (also referred to as the amount ofdepression of the brake pedal or a brake opening degree). The vehiclespeed sensor 28 senses a traveling speed of the vehicle. The hybrid ECU24 transmits and receives control signals and data signals relative toan engine ECU 29, a first MG ECU 30 and a second MG ECU 31. The engineECU 29 controls operation of the engine 10. The first MG ECU 30 controlsthe first inverter 21 to control the first MG 11. The second MG ECU 31controls the second inverter 22 to control the second MG 12. The engineECU 29, the first MG ECU 30 and the second MG ECU 31 control the engine10, the first MG 11 and the second MG 12, respectively, based on thedriving state (driving condition) of the vehicle.

For example, at the time of driving the vehicle in the normal drivemode, the drive force of the engine 10 is divided to two systems, i.e.,the rotatable shaft of the ring gear R and the rotatable shaft of thesun gear S of the first planetary gear mechanism 13. Also, at this time,the drive force of the rotatable shaft of the sun gear S of the firstplanetary gear mechanism 13 is divided and conducted to the rotatableshaft of the sun gear S of the second planetary gear mechanism 14 andthe first MG 11. In this way, the first MG 11 is driven to generate theelectric power. Also, at this time, the electric power, which isgenerated by the first MG 11, is used to drive the second MG 12, so thatthe drive force of the second MG 12 is conducted to the rotatable shaftof the ring gear R of the second planetary gear mechanism 14. The driveforce of the rotatable shaft of the ring gear R of the first planetarygear mechanism 13 and the drive force of the rotatable shaft of theplanetary carrier C of the second planetary gear mechanism 14 are bothconducted to the drive force output shaft 17 to drive the wheels 20through the drive force output shaft 17 and thereby to drive thevehicle. Furthermore, at the time of rapidly accelerating the vehicle,the electric power is supplied from the battery 23 to the second MG 12in addition to the electric power generated at the first MG 11, so thatthe electric power supplied to the second MG 12 for driving the same isincreased.

At the time of starting the traveling of the vehicle or at the time of alow load driving state of the vehicle (an operational range of theengine 10, in which a fuel efficiency is low), the engine 10 ismaintained in an engine stop state, and the first MG 11 and/or thesecond MG 12 are driven with the electric power supplied from thebattery 23 to drive the wheels 20 with the drive forces of the first MG11 and/or the second MG 12, so that the vehicle is driven in the EVdrive mode (the drive mode for driving the vehicle only with theelectric motor power provided by the first MG 11 and the second MG 12powered by the battery output of the battery 23). At the time ofdecelerating the vehicle, the second MG 12 is driven with the driveforce of the wheels 20, and thereby the second MG 12 is operated as theelectric generator. Thus, the kinetic energy of the vehicle is convertedinto the electric power through the second MG 12, and the thus generatedelectric power is stored in the battery 23. In this way, the kineticenergy of the vehicle is recovered.

In the hybrid vehicle, which has the engine 10 and the two MGs 11, 12,it is demanded to achieve three objectives, i.e., (1) controlling of therotational speed of the engine, (2) controlling of the output torque(i.e., the torque of the drive force output shaft 17) and (3) limitingof the input and output of the electric power at the battery 23, bycontrolling the two MGs 11, 12.

Therefore, according to the first embodiment, the respective routines ofFIGS. 4 to 9, which will be described later, are executed by the hybridECU 24. Specifically, the hybrid ECU 24 computes a torque (hereinafterreferred to as an engine shaft demand MG torque), which is required bythe engine shaft 16 and is provided from the first and second MGs 11, 12to control the engine rotational speed, and a torque (hereinafterreferred to as an output shaft demand MG torque), which is required bythe drive force output shaft 17 and is provided from the first andsecond MGs 11, 12 to provide the required drive force of the vehicle andto limit the input and output of the electric power at the battery 23.Then, the hybrid ECU 24 computes a torque command value of the first MG11 and a torque command value of the second MG 12 by using an equationof torque equilibrium (an equation (1) described later), whichcorresponds to the drive force transmission arrangement 15, based on theengine shaft demand MG torque and the output shaft demand MG torquediscussed above. In this way, the torque command value of the first MG11 and the torque command value of the second MG 12, which are requiredto achieve the three objectives, i.e., the controlling of the rotationalspeed of the engine, the controlling of the output torque and thelimiting of the input and output of the electric power at the battery,can be relatively easily set, and thereby the torque of the first MG 11and the torque of the second MG 12 can be cooperatively controlled.

Now, with reference to a block diagram shown in FIGS. 2 and 3, a methodof computing the torque command value of the first MG 11 and the torquecommand value of the second MG 12, will be schematically described.

As shown in FIG. 2, a target drive output shaft torque computing unit 32computes a target drive output shaft torque based on, for example, thevehicle speed (the vehicle speed sensed with the vehicle speed sensor28), the degree of depression of the accelerator pedal (morespecifically, information, i.e., a corresponding value that directly orindirectly indicates the degree of depression of the accelerator pedalsensed with the accelerator sensor 25), the shift position (the shiftposition sensed with the shift switch 26) and the degree of depressionof the brake pedal (more specifically, information, i.e., acorresponding value that directly or indirectly indicates the degree ofdepression of the brake pedal sensed with the brake sensor 27), throughuse of, for example, a map. The target drive output shaft torque is atarget drive torque of the drive force output shaft 17. The target driveoutput shaft torque will be a positive value when the torque is exertedin a driving direction of the drive force output shaft 17. In contrast,the target drive output shaft torque will be a negative value when thetorque is exerted in a braking direction of the drive force output shaft17.

Furthermore, a rotational speed computing unit 33 computes a drive forceoutput shaft rotational speed Np (a rotational speed of the drive forceoutput shaft 17) based on the vehicle speed. Then, a target drive powercomputing unit 34 obtains a target drive power by multiplying the targetdrive output shaft torque by the drive force output shaft rotationalspeed Np.

Furthermore, a drive source distribution computing unit 35 computes atarget engine output Ped of the engine 10 and a target battery outputPbd of the battery 23 as follows. First of all, at the drive sourcedistribution computing unit 35, a total vehicle losing power is computedbased on, for example, the target drive output shaft torque withreference to a map. Thereafter, a total demand power Ptotal is computedby adding the total vehicle losing power to the target drive power.Furthermore, the target battery output Pbd is computed according to thestate of the vehicle. Then, the target engine output Ped is computed bysubtracting the target battery output Pbd from the total demand powerPtotal.

Furthermore, a target engine rotational speed computing unit (alsosimply referred to as a target engine speed computing unit) 36 computesa target engine rotational speed Ned of the engine 10 (more specificallythe engine shaft 16) based on the target engine output Ped through useof, for example, a map. Thereafter, a feedback (F/B) control unit 37computes an engine shaft demand MG torque Tem of the engine 10 in amanner that reduces (or minimizes) a difference between the targetengine rotational speed Ned and an actual engine rotational speed Ne ofthe engine 10 (more specifically the engine shaft 16). In this way, theengine shaft demand MG torque Tem, which is required to control theactual engine rotational speed Ne to the target engine rotational speedNed, can be accurately computed. Thereafter, an actual engine outputestimating unit 38 computes an actual engine output Pe (estimate value)of the engine 10 after execution of the F/B control operation bymultiplying the engine shaft demand MG torque Tem by the actual enginerotational speed Ne.

Furthermore, a mechanical brake torque computing unit 39 computes amechanical brake torque (or simply referred to as a brake torque) basedon, for example, the vehicle speed and/or the degree of depression ofthe brake pedal (more specifically, the information that directly orindirectly indicates the degree of depression of the brake pedal)through use of, for example, a map. Thereafter, an output shaft demandtorque computing unit 40 computes an output shaft demand torque Tp bysubtracting the mechanical brake torque from the target drive outputshaft torque. In this way, the output shaft demand torque Tp, which is atorque required by the drive force output shaft 17 to ensure supply of arequired drive force of the vehicle, can be accurately computed.Furthermore, an electric system loss computing unit 41 computes anelectric system loss of, for example, the first and second MGs 11, 12,the first and second inverters 21, 22 and the battery 23 in conformitywith the state of the vehicle.

Furthermore, a battery output estimate value computing unit 42 computesa battery output estimate value Pb by adding the electric system lossand a difference (i.e., Ped−Pe) between the target engine output Ped andthe actual engine output Pe to the target battery output Pbd. Thebattery output estimate value Pb is an output estimate value of thebattery 23.

Also, a battery limiting unit 43 computes an output shaft power limitamount Ppg as follows. First of all, a battery output limit value, whichis an output limit value of the battery 23, is computed based on a stateof the battery 23 (e.g., a charge state and/or a temperature of thebattery 23) through use of, for example, a map. In this case, adischarging-side output limit value (a positive value) and acharging-side output limit value (a negative value) are computed as thebattery output limit values. Then, an excess amount of the batteryoutput estimative value Pb relative to the battery output limit value(the discharging-side output limit value or the charging-side outputlimit value) is computed as the output shaft power limit amount Ppg.

Thereafter, an output shaft torque limit amount computing unit 44computes an output shaft torque limit amount Tpg by dividing the outputshaft power limit amount Ppg by the drive force output shaft rotationalspeed Np. In this way, the output shaft torque limit amount Tpg, whichis a torque limit amount of the drive force output shaft 17 and isrequired to limit the input and output of the electric power to thebattery 23, can be accurately computed. Then, an output shaft demand MGtorque computing unit 45 computes an output shaft demand MG torque Tpmby subtracting the output shaft torque limit amount Tpg from the outputshaft demand torque Tp. In this way, the output shaft demand MG torqueTpm, which is required to limit the input and output of the electricpower to the battery 23, is accurately computed while providing therequired drive force of the vehicle.

Furthermore, in a case where the output shaft torque limit amount Tpg issmaller than zero (i.e., Tpg<0), a mechanical brake torque correctingunit 46 computes a command mechanical brake torque by adding the outputshaft torque limit amount Tpg to the mechanical brake torque. When theoutput shaft torque limit amount Tpg is equal to or larger than zero((Tpg≧0), the mechanical brake torque correcting unit 46 sets thecommand mechanical torque to the value of the mechanical torque. Themechanical brake is controlled based on this command mechanical braketorque.

After the computation of the engine shaft demand MG torque Tem and theoutput shaft demand MG torque Tpm, in a case where it is determined thatthe vehicle is not in the EV drive mode through a switch unit (servingas a setting section) 47 based on an EV drive flag, and it is determinedthat the engine 10 is not in a cranking state, i.e., an engine startingstate, in which the engine 10 is cranking, through a switch unit(serving as a setting section) 48 based on a cranking flag, the engineshaft demand MG torque Tem, which is computed at the F/B control unit37, is directly used.

In contrast, when it is determined that the vehicle is in the EV drivemode through the switch unit 47, the engine shaft demand MG torque Temis set to zero (i.e., Tem=0) at the switch unit 47. In this way, at thetime of driving the vehicle in the EV drive mode, it is possible tolimit an increase in the loss caused by the driving of the engine 10,which is in the engine stop state (combustion stop state), by the driveforce provided by the first and second MGs 11, 12.

Furthermore, in the case where it is determined that the engine 10 is inthe cranking state, i.e., the engine starting state through the switchunit 48, the engine shaft demand MG torque Tem is set to a value of acranking torque Tcr (i.e., Tem=Tcr) at the switch unit 48. This crankingtorque (also referred to as a required cranking torque) Tcr is a torquerequired for the cranking of the engine 10. A cranking torque computingunit 49 computes the cranking torque Tcr based on the actual enginerotational speed Ne through use of, for example, a map. Thereby, theengine 10 can be reliably started by cranking the engine with the driveforce provided by the first and second MGs 11, 12.

Thereafter, an MG torque command value computing unit 50 computes thetorque command value Tmg1 of the first MG 11 and the torque commandvalue Tmg2 of the second MG 12 through use of the equation of torqueequilibrium, which corresponds to the drive force transmissionarrangement 15, based on the engine shaft demand MG torque Tem and theoutput shaft demand MG torque Tpm.

In this instance, the following equation (1) is used as the equation oftorque equilibrium, which corresponds to the drive force transmissionarrangement 15.

$\begin{matrix}{\begin{bmatrix}{{Tmg}\; 1} \\{{Tmg}\; 2}\end{bmatrix} = {\begin{bmatrix}\frac{- \left( {{\rho 1} + {\rho 1\rho 2} + {\rho 2}} \right)}{\left( {1 + {\rho 1}} \right)\left( {1 + {\rho 2}} \right)} & \frac{- {{\rho 2}\left( {1 + {\rho 1}} \right)}}{\left( {1 + {\rho 1}} \right)\left( {1 + {\rho 2}} \right)} \\\frac{- 1}{\left( {1 + {\rho 1}} \right)\left( {1 + {\rho 2}} \right)} & \frac{- \left( {1 + {\rho 1}} \right)}{\left( {1 + {\rho 1}} \right)\left( {1 + {\rho 2}} \right)}\end{bmatrix}\begin{bmatrix}{Tem} \\{Tpm}\end{bmatrix}}} & {{Equation}\mspace{14mu} (1)}\end{matrix}$

Here, ρ1 denotes a planetary ratio (a ratio between the number of theteeth of the sun gear S and the number of the teeth of the ring gear R)of the first planetary gear mechanism 13, and ρ2 denotes a planetaryratio (a ratio between the number of the teeth of the sun gear S and thenumber of the teeth of the ring gear R) of the second planetary gearmechanism 14.

The torque of the first MG 11 and the torque of the second MG 12 arecontrolled based on the torque command value Tmg1 of the first MG 11 andthe torque command value Tmg2 of the second MG 12, respectively.

In the present embodiment, the computation of the torque command valuesof the first and second MGs 11, 12 is executed by the hybrid ECU 24according to the respective routines shown in FIGS. 4 to 9. Theprocedure of each of these routines will now be described in detail.

An engine shaft demand MG torque computation routine of FIG. 4 isexecuted repeatedly at predetermined time intervals during a powersource ON time period of the hybrid ECU 24 (a time period, during whichan electric power source of the hybrid ECU 24 is turned on) and servesas an engine shaft demand motor generator torque computing section (anengine shaft demand motor generator torque computing means) of thehybrid ECU 24. When the present routine is started, the operationproceeds to step 101. At step 101, it is determined whether the engine10 is in the cranking state (the engine starting state). When it isdetermined that the engine 10 is not in the cranking state (the enginestarting state) at step 101, the operation proceeds to step 102. At step102, it is determined whether the vehicle is in the EV drive mode.

When it is determined that the vehicle is not in the EV drive mode atstep 102, the operation proceeds to step 103. At step 103, the targetengine rotational speed Ned is computed based on the target engineoutput Ped with reference to the map of the target engine rotationalspeed Ned. The map of the target engine rotational speed Ned is formedin advance based on, for example, the test data and/or the design dataand is stored in the ROM of the hybrid ECU 24.

Thereafter, the operation proceeds to step 104. At step 104, the actualengine rotational speed Ne, which is sensed with the engine rotationalspeed sensor (not shown), is obtained. Then, the operation proceeds tostep 105. At step 105, a difference dNe between the target enginerotational speed Ned and the actual engine rotational speed Ne iscomputed.

dNe=Ned−Ne

Thereafter, the operation proceeds to step 106. At step 106, aproportional Tep of the F/B control operation is computed through use ofthe following equation based on the difference dNe and a proportionalgain Kp.

Tep=Kp×dNe

Thereafter, the operation proceeds to step 107. At step 107, an integralTei of the F/B control operation is computed through use of thefollowing equation based on the difference dNe and an integral gain Ki.

Tei=Ki×∫dNe

Thereafter, the operation proceeds to step 108. At step 108, the engineshaft demand MG torque Tem is computed through use of the followingequation based on the proportional Tep and the integral Tei.

Tem=Tep+Tei

When it is determined that the engine 10 is in the cranking state atstep 101, the operation proceeds to step 109. At step 109, the actualengine rotational speed Ne, which is sensed with the engine rotationalspeed sensor (not shown), is obtained. Thereafter, the operationproceeds to step 110. At step 110, the cranking torque Tcr (the torquerequired to crank the engine 10) is computed based on the actual enginerotational speed Ne with reference to a map of the cranking torque Tcr.The map of the cranking torque Tcr is formed in advance based on, forexample, the test data and/or the design data and is stored in the ROMof the hybrid ECU 24.

Thereafter, the operation proceeds to step 111. At step 111, the engineshaft demand MG torque Tem is set to the value of the cranking torqueTcr.

Tem=Tcr

Furthermore, at step 102, when it is determined that the vehicle is inthe EV drive mode, the operation proceeds to step 112. At step 112, theengine shaft demand MG torque Tem is set to zero (0).

Tem=0

An output shaft demand MG torque computation routine of FIG. 5 isexecuted repeatedly at predetermined time intervals during the powersource ON time period of the hybrid ECU 24 and serves as an output shaftdemand motor generator torque computing section (an output shaft demandmotor generator torque computing means) of the hybrid ECU 24. When thepresent routine is started, at step 201, the target drive output shafttorque is computed based on, for example, the vehicle speed, the degreeof depression of the accelerator pedal (more specifically, theinformation that directly or indirectly indicates the degree ofdepression of the accelerator pedal), the shift position and the degreeof depression of the brake pedal (more specifically, the informationthat directly or indirectly indicates the degree of depression of thebrake pedal) in view of the map of the target drive output shaft torque.The target drive output shaft torque will be the positive value when thetorque is exerted in the driving direction of the drive force outputshaft 17. In contrast, the target drive output shaft torque will be thenegative value when the torque is exerted in the braking direction ofthe drive force output shaft 17. The map of the target drive outputshaft torque is formed in advance based on, for example, the test dataand/or the design data and is stored in the ROM of the hybrid ECU 24.

Thereafter, the operation proceeds to step 202. At step 202, themechanical brake torque is computed based on, for example, the vehiclespeed and the degree of depression of the brake pedal (morespecifically, the information that directly or indirectly indicates thedegree of depression of the brake pedal) with reference to the map ofthe mechanical brake torque. The map of the mechanical brake torque isformed in advance based on, for example, the test data and/or the designdata and is stored in the ROM of the hybrid ECU 24.

Thereafter, the operation proceeds to step 203. At step 203, the outputshaft demand torque Tp is computed by subtracting the mechanical braketorque from the target drive output shaft torque.

Tp=Target drive output shaft torque−Mechanical brake torque

Then, the operation proceeds to step 204. At step 204, a drive sourcedistribution routine of FIG. 6 described later is executed to computethe target battery output Pbd and the target engine output Ped.

Thereafter, the operation proceeds to step 205. At step 205, the actualengine output Pe (the estimate value) after the feedback controloperation is computed by multiplying the engine shaft demand MG torqueTem by the actual engine rotational speed Ne.

Pe=Tem×Ne

Then, the operation proceeds to step 206. At step 206, the electricsystem loss of, for example, the first and second MGs 11, 12, the firstand second inverters 21, 22 and the battery 23 in conformity with thestate of the vehicle, is computed with reference to the map of theelectric system loss. The map of the electric system loss is formed inadvance based on, for example, the test data and/or the design data andis stored in the ROM of the hybrid ECU 24.

Then, the operation proceeds to step 207. At step 207, the batteryoutput estimate value Pb is computed by adding the electric system lossand the difference (i.e., Ped−Pe) between the target engine output Pedand the actual engine output Pe to the target battery output Pbd.

Pb=Pbd+(Ped−Pe)+Electric system loss

Thereafter, the operation proceeds to step 208. At step 208, the batteryoutput limit value is computed based on the charge state and/or thetemperature of the battery 23 with reference to the map of the batteryoutput limit value. In this case, the discharging-side output limitvalue (the positive value) and the charging-side output limit value (thenegative value) are computed as the battery output limit values. The mapof the battery output limit value is formed in advance based on, forexample, the test data and/or the design data and is stored in the ROMof the hybrid ECU 24.

Thereafter, the operation proceeds to step 209. At step 209, the outputshaft torque limit amount Tpg is computed by executing an output shafttorque limit amount computation routine of FIG. 7 described later.

Then, the operation proceeds to step 210. At step 210, the output shaftdemand MG torque Tpm is computed by subtracting the output shaft torquelimit amount Tpg from the output shaft demand torque Tp.

Tpm=Tp−Tpg

The drive source distribution routine of FIG. 6 (serving as a drivesource distributing section of the hybrid ECU 24) is a sub-routineexecuted at step 204 of the output shaft demand MG torque computationroutine of FIG. 5. When the present routine is started, the operationproceeds to step 301. At step 301, the target drive power is computed bymultiplying the target drive output shaft torque by the drive forceoutput shaft rotational speed Np (the rotational speed of the driveforce output shaft 17), which is obtained based on the vehicle speed.

Target drive power=Target drive output shaft torque×Np

Thereafter, the operation proceeds to step 302. At step 302, the totalvehicle losing power is computed based on, for example, the vehiclespeed and the target drive output shaft torque with reference to the mapof the total vehicle losing power. The map of the total vehicle losingpower is formed in advance based on, for example, the test data and/orthe design data and is stored in the ROM of the hybrid ECU 24.

Thereafter, the operation proceeds to step 303. At step 303, the totaldemand power Ptotal is computed by adding the total vehicle losing powerto the target drive power.

Ptotal=Target drive power+Total vehicle losing power

Then, the operation proceeds to step 304. At step 304, the targetbattery output Pbd is computed based on the vehicle state. In this case,for example, at the time of driving the vehicle in the EV drive mode,the target battery output Pbd is set to the value of the total demandpower Ptotal. Furthermore, at the time of assisting the acceleration ofthe vehicle, the target battery output Pbd is set to a predeterminedvalue P1 (0<P1<Ptotal). Furthermore, at the time of charging thebattery, the target battery output Pbd is set to a predetermined valueP2 (P2<0).

Thereafter, the operation proceeds to step 305. At step 305, the targetengine output Ped is computed by subtracting the target battery outputPbd from the total demand power Ptotal.

Ped=Ptotal−Pbd

The output shaft torque limit amount computation routine of FIG. 7(serving as an output shaft torque limit amount computing section of thehybrid ECU 24) is a sub-routine executed at step 209 of the output shaftdemand MG torque computation routine of FIG. 5. When the present routineis started, the operation proceeds to step 401. At step 401, it isdetermined whether the battery output estimate value Pb is smaller thanthe discharging-side output limit value. When it is determined that thebattery output estimate value Pb is smaller than the discharging-sideoutput limit value at step 401, the operation proceeds to step 402. Atstep 402, it is determined whether the battery output estimate value Pbis larger than the charging-side output limit value.

In the case where it is determined that the battery output estimatevalue Pb is smaller than the discharging-side output limit value at step401, and it is determined that the battery output estimate value Pb islarger than the charging-side output limit value at step 402, theoperation proceeds to step 403. At step 403, the output shaft torquelimit amount Tpg is set to zero (0).

Tpg=0

In contrast, when it is determined that the battery output estimatevalue Pb is equal to or larger than the discharging-side output limitvalue at step 401, the operation proceeds to step 404. At step 404, theoutput shaft power limit amount Ppg is computed by subtracting thedischarging-side output limit value from the battery output estimatevalue Pb.

Ppg=Pb−Discharging-side output limit value

Thereafter, the operation proceeds to step 405. At step 405, the outputshaft torque limit amount Tpg is computed by dividing the output shaftpower limit amount Ppg by the drive force output shaft rotational speedNp.

Tpg=Ppg/Np

In contrast, when it is determined that the battery output estimatevalue Pb is equal to or smaller than the charging-side output limitvalue at step 402, the operation proceeds to step 406. At step 406, theoutput shaft power limit amount Ppg is computed by subtracting thecharging-side output limit value from the battery output estimate valuePb.

Ppg=Pb−Charging-side output limit value

Thereafter, the operation proceeds to step 407. At step 407, the outputshaft torque limit amount Tpg is computed by dividing the output shaftpower limit amount Ppg by the drive force output shaft rotational speedNp.

Tpg=Ppg/Np

A mechanical brake cooperative control routine of FIG. 8 (serving as amechanical brake cooperative controlling section of the hybrid ECU 24)is repeatedly executed during the power source ON time period of thehybrid ECU 24. When the present routine is started, the operationproceeds to step 501. At step 501, the mechanical brake torque iscomputed based on, for example, the vehicle speed and the degree ofdepression of the brake pedal (more specifically, the information thatdirectly or indirectly indicates the degree of depression of the brakepedal) with reference to the map of the mechanical brake torque. The mapof the mechanical brake torque is formed in advance based on, forexample, the test data and/or the design data and is stored in the ROMof the hybrid ECU 24.

Thereafter, the operation proceeds to step 502. At step 502, it isdetermined whether the output shaft torque limit amount Tpg is smallerthan zero. When it is determined that the output shaft torque limitamount Tpg is smaller than zero at step 502, the operation proceeds tostep 503. At step 503, the command mechanical brake torque is computedby adding the output shaft torque limit amount Tpg to the mechanicalbrake torque.

Command mechanical brake torque=Mechanical brake torque+Tpg

When it is determined that the output shaft torque limit amount Tpg isequal to or larger than zero at step 502, the operation proceeds to step504. At step 504, the command mechanical brake torque is set (computed)to the value of the mechanical brake torque.

Command mechanical brake torque=Mechanical brake torque

An MG torque command value computation routine of FIG. 9 is executedrepeatedly at predetermined time intervals during the power source ONtime period of the hybrid ECU 24 and serves as a motor generator torquecommand value computing section (a motor generator torque command valuecomputing means) of the hybrid ECU 24. When the present routine isstarted, the operation proceeds to step 601. At step 601, the engineshaft demand MG torque Tem, which is computed at the engine shaft demandMG torque computation routine of FIG. 4, is retrieved, i.e., obtained.Then, the operation proceeds to step 602. At step 602, the output shaftdemand MG torque Tpm, which is computed at the output shaft demand MGtorque computation routine of FIG. 5, is retrieved, i.e., is obtained.

Thereafter, the operation proceeds to step 603. At step 603, the torquecommand value Tmg1 of the first MG 11 and the torque command value Tmg2of the second MG 12 are computed through use of the above equation (1)based on the engine shaft demand MG torque Tem and the output shaftdemand MG torque Tpm. As noted above, the above equation (1) is theequation of torque equilibrium, which corresponds to the drive forcetransmission arrangement 15.

In the first embodiment described above, first of all, the engine shaftdemand MG torque and the output shaft demand MG torque are computed. Theengine shaft demand MG torque is the torque required by the engine shaft16 and is provided from the first and second MGs 11, 12 to control theengine rotational speed. The output shaft demand MG torque is the torquerequired by the drive force output shaft 17 and is provided from thefirst and second MGs 11, 12 to limit the input and output of theelectric power at the battery 23. Then, the torque command value of thefirst MG 11 and the torque command value of the second MG 12 arecomputed through use of the equation of torque equilibrium, whichcorresponds to the drive force transmission arrangement 15, based on theengine shaft demand MG torque and the output shaft demand MG torque.Therefore, it is possible to easily set the torque command value of thefirst MG 11 and the torque command value of the second MG 12, which arerequired to achieve the three objectives, i.e., the controlling of therotational speed of the engine, the controlling of the output torque andthe limiting of the input and output of the electric power at thebattery 23, so that the torques of the first and second MGs 11, 12 canbe cooperatively controlled. Thereby, the three objectives, i.e., thecontrolling of the rotational speed of the engine, the controlling ofthe output torque and the limiting of the input and output of theelectric power at the battery 23 can be achieved without complicatingthe control operation of the first and second MGs 11, 12.

Furthermore, in the first embodiment, the planetary gear mechanisms 13,14 are used as the drive-force dividing mechanisms of the drive forcetransmission arrangement 15. Therefore, the structure of the drive forcetransmission arrangement 15 is simplified to enable the low costs.

The positional relationship of each of the sun gear S, the ring gear Rand the planetary carrier C of each planetary gear mechanism relative tothe corresponding shaft (the corresponding one of the engine shaft, thedrive force output shaft and the rotatable shaft of the MG) is notlimited to the one shown in FIG. 1. That is, the combination of eachshaft (each of the engine shaft, the drive force output shaft and therotatable shaft of the MG) and the corresponding one of the sun gear S,the ring gear R and the planetary carrier C of the correspondingplanetary gear mechanism is not limited to the one shown in FIG. 1 andmay be modified in any appropriate manner within the principle of thepresent disclosure.

Next, second to ninth embodiments of the present disclosure will bedescribed with reference to FIGS. 10 to 20. In the followingdescription, components, which are similar to those of the firstembodiment, will be indicated by the same reference numerals and willnot be described redundantly for the sake of simplicity.

Second Embodiment

In a second embodiment of the present disclosure, as shown in FIG. 10,the drive force transmission arrangement 51 is constructed as follows.That is, the engine shaft 16, the planetary carrier C of the firstplanetary gear mechanism 13 and the sun gear S of the second planetarygear mechanism 14 are interconnected with each other in a manner thatenables conduction of the drive force therebetween. The ring gear R ofthe first planetary gear mechanism 13 and the rotatable shaft 11 a ofthe first MG 11 are interconnected with each other in a manner thatenables conduction of the drive force therebetween. Furthermore, the sungear S of the first planetary gear mechanism 13, the planetary carrier Cof the second planetary gear mechanism 14 and the drive force outputshaft 17 are interconnected with each other in a manner that enablesconduction of the drive force therebetween. The ring gear R of thesecond planetary gear mechanism 14 and the rotatable shaft 12 a of thesecond MG 12 are interconnected with each other in a manner that enablesconduction of the drive force therebetween.

In the second embodiment, at the time of computing the torque commandvalue Tmg1 of the first MG 11 and the torque command value Tmg2 of thesecond MG 12 through use of the equation of torque equilibrium, whichcorresponds to the drive force transmission arrangement 51, based on theengine shaft demand MG torque Tem and the output shaft demand MG torqueTpm, the hybrid ECU 24 uses the following equation (2) as the equationof torque equilibrium, which corresponds to the drive force transmissionarrangement 51.

$\begin{matrix}{\begin{bmatrix}{{Tmg}\; 1} \\{{Tmg}\; 2}\end{bmatrix} = {\begin{bmatrix}\frac{- {{\rho 1}\left( {1 + {\rho 2}} \right)}}{1 + {\rho 1} + {\rho 1\rho 2}} & \frac{- {\rho 1\rho 2}}{1 + {\rho 1} + {\rho 1\rho 2}} \\\frac{- 1}{1 + {\rho 1} + {\rho 1\rho 2}} & \frac{{- 1} - {\rho 1}}{1 + {\rho 1} + {\rho 1\rho 2}}\end{bmatrix}\begin{bmatrix}{Tem} \\{Tpm}\end{bmatrix}}} & {{Equation}\mspace{14mu} (2)}\end{matrix}$

The positional relationship of each of the sun gear S, the ring gear Rand the planetary carrier C of each planetary gear mechanism relative tothe corresponding shaft (the corresponding one of the engine shaft, thedrive force output shaft and the rotatable shaft of the MG) is notlimited to the one shown in FIG. 10. That is, the combination of eachcorresponding shaft (each of the engine shaft, the drive force outputshaft and the rotatable shaft of the MG) and the corresponding one ofthe sun gear S, the ring gear R and the planetary carrier C of thecorresponding planetary gear mechanism is not limited to the one shownin FIG. 10 and may be modified in any appropriate manner within theprinciple of the present disclosure.

Third Embodiment

In a third embodiment of the present disclosure, as shown in FIG. 11,the drive force transmission arrangement 52 is constructed as follows.That is, the engine shaft 16 and the planetary carrier C of the firstplanetary gear mechanism 13 are interconnected with each other in amanner that enables conduction of the drive force therebetween. The sungear S of the first planetary gear mechanism 13 and the rotatable shaft11 a of the first MG 11 are interconnected with each other in a mannerthat enables conduction of the drive force therebetween. Furthermore,the ring gear R of the first planetary gear mechanism 13, the rotatableshaft 12 a of the second MG 12 and the drive force output shaft 17 areinterconnected with each other in a manner that enables conduction ofthe drive force therebetween.

In the third embodiment, at the time of computing the torque commandvalue Tmg1 of the first MG 11 and the torque command value Tmg2 of thesecond MG 12 through use of the equation of torque equilibrium, whichcorresponds to the drive force transmission arrangement 52, based on theengine shaft demand MG torque Tem and the output shaft demand MG torqueTpm, the hybrid ECU 24 uses the following equation (3) as the equationof torque equilibrium, which corresponds to the drive force transmissionarrangement 52.

$\begin{matrix}{\begin{bmatrix}{{Tmg}\; 1} \\{{Tmg}\; 2}\end{bmatrix} = {\begin{bmatrix}\frac{- \rho}{1 + \rho} & 0 \\\frac{- 1}{1 + \rho} & {- 1}\end{bmatrix}\begin{bmatrix}{Tem} \\{Tpm}\end{bmatrix}}} & {{Equation}\mspace{14mu} (3)}\end{matrix}$

The positional relationship of each of the sun gear S, the ring gear Rand the planetary carrier C of the planetary gear mechanism relative tothe corresponding shaft (the corresponding one of the engine shaft, thedrive force output shaft and the rotatable shaft of the MG) is notlimited to the one shown in FIG. 11. That is, the combination of eachshaft (each of the engine shaft, the drive force output shaft and therotatable shaft of the MG) and the corresponding one of the sun gear S,the ring gear R and the planetary carrier C of the planetary gearmechanism is not limited to the one shown in FIG. 11 and may be modifiedin any appropriate manner within the principle of the presentdisclosure.

Fourth Embodiment

In a fourth embodiment of the present disclosure, as shown in FIG. 12,the drive force transmission arrangement 53 is constructed as follows.That is, the engine shaft 16, the rotatable shaft 11 a of the first MG11 and the ring gear R of the first planetary gear mechanism 13 areinterconnected with each other in a manner that enables conduction ofthe drive force therebetween. The sun gear S of the first planetary gearmechanism 13 and the rotatable shaft 12 a of the second MG 12 areinterconnected with each other in a manner that enables conduction ofthe drive force therebetween. Furthermore, the planetary carrier C ofthe first planetary gear mechanism 13 and the drive force output shaft17 are interconnected with each other in a manner that enablesconduction of the drive force therebetween.

The positional relationship of each of the sun gear S, the ring gear Rand the planetary carrier C of the planetary gear mechanism relative tothe corresponding shaft (the corresponding one of the engine shaft, thedrive force output shaft and the rotatable shaft of the MG) is notlimited to the one shown in FIG. 12. That is, the combination of eachshaft (each of the engine shaft, the drive force output shaft and therotatable shaft of the MG) and the corresponding one of the sun gear S,the ring gear R and the planetary carrier C of the planetary gearmechanism is not limited to the one shown in FIG. 12 and may be modifiedin any appropriate manner within the principle of the presentdisclosure.

Fifth Embodiment

In a fifth embodiment of the present disclosure, as shown in FIG. 13,the drive force transmission arrangement 54 is constructed as follows.That is, the engine shaft 16 and the planetary carrier C of the firstplanetary gear mechanism 13 are interconnected with each other in amanner that enables conduction of the drive force therebetween. The sungear S of the first planetary gear mechanism 13 and the rotatable shaft11 a of the first MG 11 are interconnected with each other in a mannerthat enables conduction of the drive force therebetween. Furthermore,the ring gear R of the first planetary gear mechanism 13 and the ringgear R of the second planetary gear mechanism 14 are interconnected witheach other in a manner that enables conduction of the drive forcetherebetween. The planetary carrier C of the second planetary gearmechanism 14 and the rotatable shaft 12 a of the second MG 12 areinterconnected with each other in a manner that enables conduction ofthe drive force therebetween. Furthermore, the sun gear S of the secondplanetary gear mechanism 14 and the drive force output shaft 17 areinterconnected with each other in a manner that enables conduction ofthe drive force therebetween.

The positional relationship of each of the sun gear S, the ring gear Rand the planetary carrier C of each planetary gear mechanism relative tothe corresponding shaft (the corresponding one of the engine shaft, thedrive force output shaft and the rotatable shaft of the MG) is notlimited to the one shown in FIG. 13. That is, the combination of eachshaft (each of the engine shaft, the drive force output shaft and therotatable shaft of the MG) and the corresponding one of the sun gear S,the ring gear R and the planetary carrier C of the correspondingplanetary gear mechanism is not limited to the one shown in FIG. 13 andmay be modified in any appropriate manner within the principle of thepresent disclosure.

Even in the second to fifth embodiments discussed above, the hybrid ECU24 computes the torque command value of the first MG 11 and the torquecommand value of the second MG 12 through use of the equation of torqueequilibrium, which corresponds to the drive force transmissionarrangement, based on the engine shaft demand MG torque and the outputshaft demand MG torque. Thereby, the three objectives, i.e., thecontrolling of the rotational speed of the engine, the controlling ofthe output torque and the limiting of the input and output of theelectric power at the battery can be achieved without complicating thecontrol operation of the first and second MGs 11, 12.

Sixth Embodiment

In a sixth embodiment of the present disclosure, as shown in FIG. 14,the drive force transmission arrangement 55 is constructed as follows.That is, a brake 56 is provided to the engine shaft 16, and the rest ofthe structure of the drive force transmission arrangement 55 is similarto the drive force transmission arrangement 15 (see FIG. 1) of the firstembodiment. Alternatively, as shown in FIG. 15, the drive forcetransmission arrangement 57 may be constructed as follows. That is, astationary-end-coupled one-way clutch 58, which is coupled to apredetermined stationary end (e.g., the housing of the drive forcetransmission arrangement 57), is provided to the engine shaft 16.

In the sixth embodiment, with reference to FIG. 16, after thecomputation of the engine shaft demand MG torque Tem and the outputshaft demand MG torque Tpm in a manner similar to that of the firstembodiment (see FIG. 2), in a case where it is determined that the brake56 or the stationary-end-coupled one-way clutch 58 is in a decoupledstate (the brake 56 or the stationary-end-coupled one-way clutch 58being switched to the side, at which the transmission of the drive forcethrough the brake 56 or the stationary-end-coupled one-way clutch 58 isnot limited) through the switch unit (serving as a setting section) 59,and it is determined that the engine 10 is not in the cranking state(the engine starting state, in which the engine 10 is cranking) throughthe switch unit (serving as the setting section) 48, the engine shaftdemand MG torque Tem, which is computed at the F/B control unit 37 (seeFIG. 2), is directly used. Thereby, the engine shaft demand MG torqueTem is computed in a manner that reduces (or minimizes) a differencebetween the target engine rotational speed and the actual enginerotational speed. In this way, in the case where it is determined thatthe brake 56 or the stationary-end-coupled one-way clutch 58 is in thedecoupled state, the engine shaft demand MG torque Tem, which isrequired to control the actual engine rotational speed to the targetengine rotational speed, can be accurately set.

In contrast, in the case where it is determined that the brake 56 or thestationary-end-coupled one-way clutch 58 is in the coupled state (thestate where the rotation of the engine shaft 16 is prevented through thebrake 56 or the stationary-end-coupled one-way clutch 58) through theswitch unit 59, the engine shaft demand MG torque Tem is set to apredetermined torque at the switch unit 59.

In such a case, for instance, 0 (zero) may be used as the predeterminedtorque to set the engine shaft demand MG torque Tem to zero (i.e.,Tem=0). In this way, in the coupled state of the brake 56 or thestationary-end-coupled one-way clutch 58, it is possible to limitapplication of an excessive load to the engine shaft 16, to which thebrake 56 or the stationary-end-coupled one-way clutch 58 is provided.

Alternatively, a constant (a target urging torque), which is other than0 (zero), may be used as the predetermined torque to set the engineshaft demand MG torque Tem to the constant (the target urging torque),which is other than 0 (zero). In this way, in the coupled state of thebrake 56 or the stationary-end-coupled one-way clutch 58, theappropriate urging torque is applied to the engine shaft 16, to whichthe brake 56 or the stationary-end-coupled one-way clutch 58 isprovided, so that generation of rotational vibration is limited.

Also, the engine shaft demand MG torque Tem may be set to a value(predetermined torque) computed by a target torque computing unit 60through use of the following equation (4). The following equation (4) isthe equation of torque equilibrium that is designed for the case wherethe engine shaft 16, to which the brake 56 or the stationary-end-coupledone-way clutch 58 is provided, serves as the stationary end.

$\begin{matrix}{{Tem} = {\frac{\left( {1 + {\rho 1}} \right)\left( {K - {\rho 2}} \right)}{{\rho 1} + {\rho 1\rho 2} + {\rho 2} - K}{Tpm}}} & {{Equation}\mspace{14mu} (4)}\end{matrix}$

In the above equation (4), K denotes a distribution coefficient of thetoque for the first MG 11 and the second MG 12.

In this way, the operational efficiencies of the first MG 11 and thesecond MG 12 can be improved by manipulating the working points of thefirst MG 11 and the second MG 12 through the manipulation of thedistribution coefficient K.

The positional relationship of each of the sun gear S, the ring gear Rand the planetary carrier C of each planetary gear mechanism relative tothe corresponding shaft (the corresponding one of the engine shaft, thedrive force output shaft and the rotatable shaft of the MG) is notlimited to the one shown in FIG. 14 or FIG. 15. That is, the combinationof each shaft (each of the engine shaft, the drive force output shaftand the rotatable shaft of the MG) and the corresponding one of the sungear S, the ring gear R and the planetary carrier C of the correspondingplanetary gear mechanism is not limited to the one shown in FIG. 14 orFIG. 15 and may be modified in any appropriate manner within theprinciple of the present disclosure.

Seventh Embodiment

In a seventh embodiment of the present disclosure, as shown in FIG. 17,the drive force transmission arrangement 61 is constructed as follows.That is, a clutch 62 is provided to the engine shaft 16 to connect ordisconnect the engine 10 relative to the planetary carrier C of thefirst planetary gear mechanism 13 through coupling or decoupling,respectively, of the clutch 62, and the rest of the structure of thedrive force transmission arrangement 61 is similar to the drive forcetransmission arrangement 15 (see FIG. 1) of the first embodiment.Alternatively, as shown in FIG. 18, the drive force transmissionarrangement 63 may be constructed as follows. That is, a one-way clutch64 is provided to the engine shaft 16 to connect or disconnect theengine 10 relative to the planetary carrier C of the first planetarygear mechanism 13 through coupling or decoupling, respectively, of theone-way clutch 64.

In the seventh embodiment, after the computation of the engine shaftdemand MG torque Tem and the output shaft demand MG torque Tpm in amanner similar to that of the first embodiment (see FIG. 2), in a casewhere it is determined that the clutch 62 or the one-way clutch 64 is ina coupled state (the clutch 62 or the one-way clutch 64 being switchedto the side, at which the transmission of the drive force is notlimited), and it is determined that the engine 10 is not in the crankingstate (the engine starting state), the engine shaft demand MG torqueTem, which is computed at the F/B control unit 37 (see FIG. 2), isdirectly used. Thereby, the engine shaft demand MG torque Tem iscomputed in a manner that reduces (or minimizes) a difference betweenthe target engine rotational speed and the actual engine rotationalspeed. In this way, in the case where the clutch 62 or the one-wayclutch 64 is in the coupled state, the engine shaft demand MG torqueTem, which is required to control the actual engine rotational speed tothe target engine rotational speed, can be accurately set.

In contrast, when it is determined that the clutch 62 or the one-wayclutch 64 is in the decoupled state (the state of disabling thetransmission of the drive force), the engine shaft demand MG torque Temis set to zero (i.e., Tem=0). In this way, when the clutch 62 or theone-way clutch 64 is in the decoupled state, it is possible to limit theunnecessary free rotation of the clutch 62 or the one-way clutch 64 andthereby to limit the occurrence of the unnecessary loss.

The positional relationship of each of the sun gear S, the ring gear Rand the planetary carrier C of each planetary gear mechanism relative tothe corresponding shaft (the corresponding one of the engine shaft, thedrive force output shaft and the rotatable shaft of the MG) is notlimited to the one shown in FIG. 17 or FIG. 18. That is, the combinationof each shaft (each of the engine shaft, the drive force output shaftand the rotatable shaft of the MG) and the corresponding one of the sungear S, the ring gear R and the planetary carrier C of the correspondingplanetary gear mechanism is not limited to the one shown in FIG. 17 orFIG. 18 and may be modified in any appropriate manner within theprinciple of the present disclosure.

Eighth Embodiment

In an eighth embodiment of the present disclosure, as shown in FIG. 19,the drive force transmission arrangement 65 is constructed as follows.That is, a clutch 66 (or a one-way clutch) is provided to the engineshaft 16 to connect or disconnect the engine 10 relative to theplanetary carrier C of the first planetary gear mechanism 13 and the sungear S of the second planetary gear mechanism 14 through coupling ordecoupling, respectively, of the clutch 66 (or the one-way clutch), andthe rest of the structure of the drive force transmission arrangement 65is similar to the drive force transmission arrangement 51 (see FIG. 10)of the second embodiment. In this case, the engine shaft demand MGtorque Tem and the output shaft demand MG torque Tpm are computed in amanner similar to that of the seventh embodiment.

Alternatively, the brake or the stationary-end-coupled one-way clutch(e.g., the brake or the stationary-end-coupled one-way clutch of thesixth embodiment) may be provided to the engine shaft 16. In such acase, the engine shaft demand MG torque Tem and the output shaft demandMG torque Tpm are computed in a manner similar to that of the sixthembodiment.

The positional relationship of each of the sun gear S, the ring gear Rand the planetary carrier C of each planetary gear mechanism relative tothe corresponding shaft (the corresponding one of the engine shaft, thedrive force output shaft and the rotatable shaft of the MG) is notlimited to the one shown in FIG. 19. That is, the combination of eachshaft (each of the engine shaft, the drive force output shaft and therotatable shaft of the MG) and the corresponding one of the sun gear S,the ring gear R and the planetary carrier C of the correspondingplanetary gear mechanism is not limited to the one shown in FIG. 19 andmay be modified in any appropriate manner within the principle of thepresent disclosure.

Ninth Embodiment

In a ninth embodiment of the present disclosure, as shown in FIG. 20,the drive force transmission arrangement 67 is constructed as follows.That is, a clutch 68 (or a one-way clutch) is provided to the engineshaft 16 to connect or disconnect the engine 10 relative to theplanetary carrier C of the first planetary gear mechanism 13 throughcoupling or decoupling, respectively, of the clutch 68 (or the one-wayclutch), and the rest of the structure of the drive force transmissionarrangement 67 is similar to the drive force transmission arrangement 52(see FIG. 11) of the third embodiment. In this case, the engine shaftdemand MG torque Tem and the output shaft demand MG torque Tpm arecomputed in a manner similar to that of the seventh embodiment.

Alternatively, the brake or the stationary-end-coupled one-way clutch(e.g., the brake or the stationary-end-coupled one-way clutch of thesixth embodiment) may be provided to the engine shaft 16. In such acase, the engine shaft demand MG torque Tem and the output shaft demandMG torque Tpm are computed in a manner similar to that of the sixthembodiment.

The positional relationship of each of the sun gear S, the ring gear Rand the planetary carrier C of the planetary gear mechanism relative tothe corresponding shaft (the corresponding one of the engine shaft, thedrive force output shaft and the rotatable shaft of the MG) is notlimited to the one shown in FIG. 20. That is, the combination of eachshaft (each of the engine shaft, the drive force output shaft and therotatable shaft of the MG) and the corresponding one of the sun gear S,the ring gear R and the planetary carrier C of the planetary gearmechanism is not limited to the one shown in FIG. 20 and may be modifiedin any appropriate manner within the principle of the presentdisclosure.

Even in the sixth to ninth embodiments discussed above, the hybrid ECU24 computes the torque command value of the first MG 11 and the torquecommand value of the second MG 12 through use of the equation of torqueequilibrium, which corresponds to the drive force transmissionarrangement, based on the engine shaft demand MG torque and the outputshaft demand MG torque. Thereby, the three objectives, i.e., thecontrolling of the rotational speed of the engine, the controlling ofthe output torque and the limiting of the input and output of theelectric power at the battery can be achieved without complicating thecontrol operation of the first and second MGs 11, 12.

In the sixth to ninth embodiments, the present disclosure is applied tothe system, which has the clutch device (i.e., the clutch 62, 66, 68,the one-way clutch 64, the brake 56 or the stationary-end-coupledone-way clutch 58) that is provided to the engine shaft 16. However, thepresent disclosure is not limited to this structure. For instance, thepresent disclosure may be applied to a system, which has the clutchdevice (the clutch device similar to the clutch device discussed in anyone of the sixth to ninth embodiments) that is provided to the driveforce output shaft 17.

In such a case, when the clutch device is switched to the side, at whichthe transmission of the drive force is not limited (i.e., when the brakeor the stationary-end-coupled one-way clutch is in the decoupled stateor when the clutch or the one-way clutch is in the coupled state), theoutput shaft demand MG torque Tpm, which is computed at the output shaftdemand MG torque computing unit 45, is directly used. In this way, theoutput shaft demand MG torque Tpm, which is required to provide therequired drive force of the vehicle and to limit the input and output ofthe electric power at the battery 23, can be accurately set.

In contrast, when it is determined that the brake or thestationary-end-coupled one-way clutch is in the coupled state (the stateof preventing the rotation of the drive force output shaft 17), theoutput shaft demand MG torque Tpm is set to the predetermined value(e.g., zero, the constant other than zero, or the value computed throughthe use of the equation of torque equilibrium, which is designed for thecase where the drive force output shaft 17 serves as the stationaryend). Alternatively, when it is determined that the clutch or theone-way clutch is in the decoupled state (the state of disabling thetransmission of the drive force), the output shaft demand MG torque Tpmis set to zero (i.e., Tpm=0).

The structure of the drive force transmission arrangement is not limitedto any one of the above embodiments and may be modified in anappropriate manner. For instance, a motor generator (MG) of a two-rotortype may be used as a drive-force dividing mechanism.

Furthermore, in each of the above embodiments, the hybrid ECU is used tocompute the engine shaft demand MG torque, the output shaft demand MGtorque and the torque command values of the MGs. However, the presentdisclosure is not limited to this. That is, any other appropriate ECU(e.g., the MG ECU), which is other than the hybrid ECU, may be used tocompute the engine shaft demand MG torque, the output shaft demand MGtorque and the torque command values of the MGs. Further alternatively,both of the hybrid ECU and the other appropriate ECU may be used tocompute the engine shaft demand MG torque, the output shaft demand MGtorque and the torque command values of the MGs.

Additional advantages and modifications will readily occur to thoseskilled in the art. The present disclosure in its broader terms istherefore not limited to the specific details, representative apparatus,and illustrative examples shown and described.

What is claimed is:
 1. A drive force output apparatus for a vehicle,comprising: an internal combustion engine; a plurality of motorgenerators; a drive force transmission arrangement that includes atleast one drive force dividing mechanism, wherein an engine shaft of theinternal combustion engine, rotatable shafts of the plurality of motorgenerators and a drive force output shaft are interconnected with eachother through the drive force transmission arrangement in a manner thatenables transmission of a drive force through the drive forcetransmission arrangement, and the drive force output shaft is connectedto a plurality of wheels of the vehicle to transmit a drive force; abattery that is connected to the plurality of motor generators to outputand receive an electric power relative to the plurality of motorgenerators; an engine shaft demand motor generator torque computingsection that computes an engine shaft demand motor generator torque,which is a torque that is provided from the plurality of motorgenerators and is required by the engine shaft of the internalcombustion engine to control a rotational speed of the internalcombustion engine; an output shaft demand motor generator torquecomputing section that computes an output shaft demand motor generatortorque, which is a torque that is provided from the plurality of motorgenerators and is required by the drive force output shaft to ensuresupply of a required drive force of the vehicle and to limit input andoutput of the battery; and a motor generator torque command valuecomputing section that computes a torque command value of each of theplurality of motor generators through use of an equation of torqueequilibrium, which corresponds to the drive force transmissionarrangement, based on the engine shaft demand motor generator torque andthe output shaft demand motor generator torque.
 2. The drive forceoutput apparatus according to claim 1, wherein the engine shaft demandmotor generator torque computing section computes the engine shaftdemand motor generator torque in a manner that reduces a differencebetween a target engine rotational speed of the internal combustionengine and an actual engine rotational speed of the internal combustionengine.
 3. The drive force output apparatus according to claim 1,further comprising a setting section that sets the engine shaft demandmotor generator torque to zero when the vehicle is driven by the driveforce provided from the plurality of motor generators in an engine stopstate of the internal combustion engine.
 4. The drive force outputapparatus according to claim 1, further comprising a setting sectionthat sets the engine shaft demand motor generator torque to a value of arequired cranking torque, which is required to crank the internalcombustion engine, at a time of starting the internal combustion engine.5. The drive force output apparatus according to claim 1, wherein theoutput shaft demand motor generator torque computing section computesthe output shaft demand motor generator torque based on: an output shaftdemand torque that is a torque, which is required by the drive forceoutput shaft to ensure the required drive force of the vehicle and iscomputed by the output shaft demand motor generator torque computingsection; and an output shaft torque limit amount that is a torque limitamount of the drive force output shaft, which is required to limit inputand output of the battery and is computed by the output shaft demandmotor generator torque computing section.
 6. The drive force outputapparatus according to claim 5, wherein: the output shaft demand motorgenerator torque computing section computes the output shaft demandtorque based on: a target drive output shaft torque that is a targetdrive torque of the drive force output shaft, which is computed by theoutput shaft demand motor generator torque computing section based atleast on information that indicates a degree of depression of anaccelerator pedal; and a mechanical brake torque, which is computed bythe output shaft demand motor generator torque computing section basedat least on information that indicates a degree of depression of a brakepedal.
 7. The drive force output apparatus according to claim 5,wherein: the output shaft demand motor generator torque computingsection computes the output shaft torque limit amount based on: abattery output estimate value, which is an output estimate value of thebattery and is computed by the output shaft demand motor generatortorque computing section based on a target battery output, an electricsystem loss of the drive force output apparatus and a difference betweena target engine output and an actual engine output of the internalcombustion engine; and a battery output limit value, which is an outputlimit value of the battery and is computed by the output shaft demandmotor generator torque computing section based on a state of thebattery.
 8. The drive force output apparatus according to claim 1,wherein the at least one drive force dividing mechanism is at least oneplanetary gear mechanism.
 9. The drive force output apparatus accordingto claim 1, wherein: at least one of the engine shaft and the driveforce output shaft is provided with a clutch device; and the clutchdevice is one of a clutch, a brake, a one-way clutch and astationary-end-coupled one-way clutch, wherein thestationary-end-coupled one-way clutch is coupled to a predeterminedstationary end.
 10. The drive force output apparatus according to claim9, wherein the engine shaft demand motor generator torque computingsection computes the engine shaft demand motor generator torque in amanner that reduces a difference between a target engine rotationalspeed of the internal combustion engine and an actual engine rotationalspeed of the internal combustion engine in a state where the clutchdevice is switched to a side, at which transmission of a drive forcethrough the clutch device is not limited.
 11. The drive force outputapparatus according to claim 9, wherein in a state where the clutchdevice is switched to a side, at which transmission of a drive forcethrough the clutch device is not limited, the output shaft demand motorgenerator torque computing section computes the output shaft demandmotor generator torque based on: an output shaft demand torque that is atorque, which is required by the drive force output shaft to ensure therequired drive force of the vehicle and is computed by the output shaftdemand motor generator torque computing section; and an output shafttorque limit amount that is a torque limit amount of the drive forceoutput shaft, which is required to limit input and output of the batteryand is computed by the output shaft demand motor generator torquecomputing section.
 12. The drive force output apparatus according toclaim 9, wherein: the clutch device is one of the clutch and the one-wayclutch; the drive force output apparatus further comprises a settingsection that sets corresponding at least one of the engine shaft demandmotor generator torque and the output shaft demand motor generatortorque, which corresponds to the at least one of the engine shaft andthe drive force output shaft that is provided with the one of the clutchand the one-way clutch; and when the one of the clutch and the one-wayclutch is in a decoupled state, the setting section sets thecorresponding at least one of the engine shaft demand motor generatortorque and the output shaft demand motor generator torque to zero. 13.The drive force output apparatus according to claim 9, wherein: theclutch device is one of the brake and the stationary-end-coupled one-wayclutch; the drive force output apparatus further comprises a settingsection that sets corresponding at least one of the engine shaft demandmotor generator torque and the output shaft demand motor generatortorque, which corresponds to the at least one of the engine shaft andthe drive force output shaft that is provided with the one of the brakeand the stationary-end-coupled one-way clutch; and when the one of thebrake and the stationary-end-coupled one-way clutch is in a coupledstate, the setting section sets the corresponding at least one of theengine shaft demand motor generator torque and the output shaft demandmotor generator torque to a predetermined torque.
 14. The drive forceoutput apparatus according to claim 13, wherein a value of thepredetermined torque is zero.
 15. The drive force output apparatusaccording to claim 13, wherein a value of the predetermined torque is aconstant, which is other than zero.
 16. The drive force output apparatusaccording to claim 13, wherein a value of the predetermined torque is acorresponding value that is computed through use of an equation oftorque equilibrium, which corresponds to a case where the at least oneof the engine shaft and the drive force output shaft, which is providedwith the one of the brake and the stationary-end-coupled one-way clutch,serves as a stationary end.